Skip to main content

While Henry finishing off installing my rear clip I plan on taking my old engine down to the shop that will be doing the rebuild. Because I'll need new barrels and piston I'm considering upgrading my 90.5s to 94s. The question I keep asking myself is, "Should I?"
I'd like the extra power/torque, but I have some concerns about longevity, leaking, and overheating. My IM will be mainly a highway cruiser/canyon carver and I plan on making a few 1000+ mile trips in the next few years.
Also, can anyone recommend a piston/barrel set (90.5 or 94)? I've looked at Mahle/Cima graphite coated 94s:
http://www.cip1.ca/ProductDetails.asp?ProductCode=ACC-C10-5172
and a true-forged kit:
http://www.cip1.ca/ProductDetails.asp?ProductCode=ACC-C10-5209
Is the extra money for the forged pistons worth it?
Thanks
Ron

1959 Intermeccanica(Convertible D)

Original Post

Replies sorted oldest to newest

While Henry finishing off installing my rear clip I plan on taking my old engine down to the shop that will be doing the rebuild. Because I'll need new barrels and piston I'm considering upgrading my 90.5s to 94s. The question I keep asking myself is, "Should I?"
I'd like the extra power/torque, but I have some concerns about longevity, leaking, and overheating. My IM will be mainly a highway cruiser/canyon carver and I plan on making a few 1000+ mile trips in the next few years.
Also, can anyone recommend a piston/barrel set (90.5 or 94)? I've looked at Mahle/Cima graphite coated 94s:
http://www.cip1.ca/ProductDetails.asp?ProductCode=ACC-C10-5172
and a true-forged kit:
http://www.cip1.ca/ProductDetails.asp?ProductCode=ACC-C10-5209
Is the extra money for the forged pistons worth it?
Thanks
Ron
A stock 1600 cc VW engine has 85.5 mm pistons and a 69mm stroke crankshaft which displaces 1584cc A 1915 cc engine has a stock stroke crankshaft of 69 mm's with the addition of 94 mm pistons.

I'm not a big fan of the 1915 cc engines as they lack stroke which creates torque.

I've built a few 94mm x 74mm engines. The extra 5mm of crank length adds a great deal of torque and because it's not a lot of extra stroke, the engine doesn't run hot and no engine case clearancing is required. In fact, stock stroke pistons can be used with .10 inch spacers.

94 x 74 equals 2054 cc's and it make driving a lot more fun. (Use only forged pistons)
Crank size isn't an concern for me, as I already have a 82 mm crank from my old 2110 engine. I'm leaning towards going with the 94s and may buy the forged 94s from Cip1, before their 15% off sale ends. My only concern is that they're made in China.
Thanks for all the advice and Merry Christmas!
Ron
76 X 94 is a 2109. I have 78 X 84, that is a 2165. I think a 82 X 94 is 2275, correct? 86 X 94 is the monster 2316.

I have Mahles in 94mm, forged pistons, Bugpack H-beam rods. Send all the rotating parts out for a DYNAMIC balance, you'll appreciate how smooth it is and thank me later. The crank, gears, spacers all installed, and the flywheel, pressure plate and front pulley should be balanced together. I would also balance the pistons, pins, and rods.

Build it right and it won't leak.
Longer stroke = more torque but you need the right combination of other factors as well. 95x74.4 is what is used in a stock 3.2 911 motor and pound for pound is a lot more torque than HP. I would see if I could use the same type of cam profile as to lift and duration and copy what works so well.........just food for thought.
A friend had been asking these questions and I was reluctant to offer answers because ,,I'm a stock kind a guy...

What heads and valves would you put with the 94's or even 96's and would you go ceramic coating on the inside of the crown and the exhaust ports to also help it?

We discussed a 72 stroke 1200 cc type crank. Putting the config. a bit more like a T4. 2056 and using 37's and 40 valves

But when yo go that big in valves you can have seat falures.
Dave, you're on the right track however trying to compare a 6 cylinder Porsche engine with a 4 cylinder VW engine doesn't work. First off, the Porsche engine is actually 3,164 cc's with the combination stated. If you could find a 74.4 x 95 VW engine it would only produce 2,109 cc's for a difference of 1,055 cc's.
The added 2 cylinders on the Porsche engine coupled with overhead cams, better head design and better fuel induction all add up to more power.

But, I've built several engines with a 74mm crank with various size of pistons and for a street car, they work great.

The 356/912 engine was rated at 1,600 cc's as was the VW.

Porsche and VW were generous in their published engine displacement as the Porsche engine only had 1,582 cc's with a bore of 82.5 cc's and a stroke of 74 cc's.

The stock 1,600 cc VW engine produced 3 more cc's at 1,585 cc's.
It had a bore of 85.5mm and a stroke of 69mm's

But remember this, regardless of which gasoline engine you're talking about, all of them have the same amount of torque and horsepower at 5,252 RPM's.

The combination of better heads, better intake/exhaust, different cam profile and twin (2) barrel carbs made it a much stronger running engine than the VW's version. In addition, the 356/912 engine was a 3 piece design as opposed the VW's 2 piece engine case.

VW's biggest downfall when dealing with aftermarket hot rod components are their heads. That's why so many people were making aftermarket cylinderheads with large intake and exhaust ports, larger valves and with re-designed intake and exhaust runners.

Anyone can assemble a VW engine but getting it to produce torque/HP is another story.

But remember this, every gasoline engine produces the same torque and horsepower numbers at 5,252 RPM's.
Larry,

I was only using the 3.2 Porsche as a comparison point to the cylinder size v rod length v what was being discussed as a possible good combination.

Just a point of info, I have been twisting wrenches for 30+ years and have been in many VW and Porsche engines.

I can not for the life of me understand this quote: "But remember this, every gasoline engine produces the same torque and horsepower numbers at 5,252 RPM's."

How can that be? Where does your data come from?

Curious here?

BTW the reason Porsche was generous in there published numbers was mostly to be in the "under 1.6L class" with their "stock" bores.
David K., you're not being anal. But, (no anal pun intended LOL) they do meet at 5,252 RPM's

David K. and Dave M. Read this: http://www.vettenet.org/torquehp.html in particular, the sub title
"The Case For Torque" It will explain what I wrote.

In addition, the formula for determining horsepower is:

horsepower = rpm x torque divided by 5252 (5,252 is the constant)

For example: Lets say that an engine produces 150 lb's of torque at 5,252 RPM's
5252 rpm's x 150 (torque) divided by 5252 (constant) = 150 Horsepower

The formula for determining Torque is:

Torque = Horsepower x 5252 divided by RPM's

For example:
Lets say that an engine produces 150 HP at 5,252 RPM's
150 (horsepower) x 5252 (constant) divided by 5,252 (rpm's) = 150 torque

By working the formula both ways, you can clearly see that 5,252 RPM's is where Torque and Horsepower will be exactly the same number.

Dave M. I wasn't knocking your knowledge only pointing out the difference between engines. Any input from any member of this board is worth reading.

Like you, I've been twisting wrenches on VW and Porsche's for a long time (45 years)

Finally, my statement should have read, gasoline and diesel engines.

Another example: My motorhome diesel engine produces 435 HP at 1,700 RPM's

435 HP x 5252 divided by 1700 (rpm's) equals 1,343 lb's of torque
(spot on to the engine manual)

1343 torque x 1700 rpm's divided by 5252 equals 435 HP.


OK, Larry now I get it. I was reading your quote saying all motors have the "same" as in the same amount for every engine. As each engine develops different amounts and if one has 150 another may have 1500 but the intersection point is the same @ 5252 RPM.

Math can drive you crazy.....;-)
Post Content
×
×
×
×
Link copied to your clipboard.
×
×